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Y-chromosome abnormalities in men with sub-fertility. An analysis of the frequency of abnormalities and determination of a threshold sperm concentration for genetic analysis

Johnson, M1; Raheem, A1; De Luca, F1; Johnson, TF1; Zainal, Y1; Poselay, S1; Hallerstrom, M1; Mohammadi, B1; Moubasher, A1; Sangster, P2; Muneer, A1; Ralph, D1

1: University College London Hospital, United Kingdom; 2: University College London Hospital

Background: Detection of microdeletions of the long arm of the Y chromosome (Yq) is common practice in men with azoospermia and severe oligozoospermia. Guidelines from the European Association of Urology recommend testing for Yq microdeletions in men with a semen concentration of <5 million/mL. We aim to describe the prevalence of Yq microdeletions in a multi-ethnic urban population in London, United Kingdom. We also aim to determine a threshold based on semen concentration (million/mL) for testing for Yq microdeletions.

Materials and Methods: We performed a retrospective cohort study on 1473 men that underwent genetic evaluation between July 2004 and December 2016. Univariate logistic regression analyses were conducted with microdeletions vs no-microdeletions as the response variable. Semen concentration, combined testicular volume, FSH, LH and testosterone were all used as predictor variables.

Results: Microdeletions of the Y-chromosome were found in 4% of our population (n = 58). Microdeletion of the AZFc region occurred in 75% of these men followed by AZFb+c in 13.8%, followed by AZFb, then AZFa and partial AZFa. Semen count was a significant predictor of the presence of a microdeletion (p = 0.035). None of the men with an AZF microdeletion had a sperm count of greater than 0.5 million/mL. We propose a reduction in the current semen count threshold at which Yq microdeletions are tested. A threshold value of 0.5 million/mL (a 10-fold reduction compared to the current guidelines), would increase the specificity without adversely affecting the sensitivity (See table 1). The cost savings of this would be significant. The sperm retrieval rate (SSR) following microdissection testicular sperm extraction was 33.2%. This rate is lower than is described in the literature.

Conclusions: The prevalence of Y chromosome microdeletions in infertile men appears to vary between populations and countries. A reduction in the current semen count threshold of testing for microdeletions of the Y-chromosome would increase the specificity, lower the relative cost without adversely affecting the sensitivity. The rate of SSR may be lower than that previously described in the literature.

Table 1. Sensitivity and specificity of different semen count threshold levels in detecting microdeletions. Relative cost of each threshold is also stated, with the relative cost at the 0.1 threshold = 1.

Semen count threshold value




Relative cost


















Work supported by industry: no.

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